Horizontal drilling machines are utilized to drill underground bore holes for utility lines and other underground pipes. Using this type of trenchless drilling minimizes disruption of surface soil. This decreases the cost of laying utility lines especially in developed areas, and also substantially decreases the possibility of damaging previously buried utility lines and other underground structures.
In most cases the drilling machine comprises a frame, a motorized drive system mounted on the frame, and a drill string connected on one end to the drive system and on the other end to a boring tool/boring head assembly. The motorized drive system provides thrust to advance the drill string through the ground according to a planned bore path.
The boring head is commonly steered using a "slant-face" drill bit or some other suitable mechanism. A radio transmitter or other tracking device such as a "beacon" encased in housing may be provided in or directly behind the boring head to permit the tracking of the boring head.
Underground boring operations involve thrusting and rotating of the boring head in rocky and abrasive soil conditions, thereby increasing the probability of damage to the component parts of the boring head. To permit removal and/or replacement of the drill bit and other components, it is desirable for the boring head to be removably attached to the end of the drill string or beacon housing. To this end many boring heads are attached by a threaded connection. However, because of high rotational impact loading exerted on such joints, it is often difficult to disengage or "break out" these threaded joints.
In addition it is difficult to utilize a threaded joint to connect a replaceable head. This is especially true when utilizing a beacon housing where the transmitter is inserted from the side for easy maintenance of the electronics and where the orientation of the head should match the "clocking" of the beacon.
Therefore, while conventional removable boring heads have provided advantages in repair and maintenance of boring head assemblies, there remains a need for a more easily detachable boring head that is used in conjunction with a radio transmitter. The present invention is directed to an improvement to boring head assemblies with removable boring heads that specifically address this problem.